A heater wherein a housing supports an element for supporting a plurality of insulators for supporting, in turn, a helical heating element is shown in U.S. Pat. No. 4,617,547 (Howard). In this heater, the central axes of the helical coils extend in the direction of the air flow, which is dictated by the shape of the housing. The housing is generally U-shaped and is secured to another U-shaped element to form a channel for directing the flow of air in the longitudinal direction of the housing.
The heater shown in U.S. Pat. No. 4,617,547 is designed to be a self supporting channel, as when two U-shaped channel parts are secured together, or to be a part of another structure, as when one U-shaped section is secured to the other structure.
The structure shown in U.S. Pat. No. 4,617,547 employs wire-like elements to support the insulating elements. It has been suggested, however, to use plates to support the insulators. Examples are found in U.S. Pat. Nos. 1,695,801 (Dibble); 1,844,678 (pickup); and 2,856,500 (Hartman).